     set
     (create user-id exercise-id)))
 
-(defn normalized-rating-sets 
+(defn normalize-rating-sets 
   "Take a collection of rating sets, normalize the ratings of each set,
    and return a single collection comprising all the normalized ratings."
   [rating-sets]

              (sql/where {:exercises_id (:id exercise)})
              (sql/with entities/ratings (sql/with entities/users))))

(def summarize (comp summarize-rating-sets normalized-rating-sets rating-sets))

(defn aggregate-ratings 
  "Given collection of ratings, take their average."
  [ratings]
  (let [summed-rating (reduce fold-sum ratings)
        count (count ratings)
        ratings-average (update-in summed-rating [:rating] #(/ % count))]
    ratings-average))

(defn summarize-rating-sets 
  "Take a collection of ratings, group them by user,
